DRV initially hoped to reunite Vietnam in accordance with the terms drawn up by 1954 Geneva Agreements, but Ngo Dinh Diem and his CIA handlers set about purging Communists in South Vietnam. So in 1959, PAVN began preparations for infiltrating South Vietnam (Ho Chi Minh Trail).

In 1968, PAVN launched offensive against ROVN; disaster, loss of non-Communist allies in the South. Rebuilt with surprising speed, despite massive US bombing ("Rolling Thunder"). In 1972, offensive reduced ROVN control to small enclaves in the South. Increased US bombing ("Linebacker") of DRV, while US Army sought to train the Army of ROVN (ARVN). US troops withdrawn March 1973, resulting in collapse, PAVN victory.